1. Field of the Invention
The invention relates to a method and a device for optimizing the contrast and the angle of view of a liquid crystal display.
It applies more particularly, but not exclusively, to transmissive type liquid crystal displays intended to be observed along a given axis of vision. Such is the case in particular in the instrument panels of vehicles, and in particular of aircraft.
2. Description of the Prior Art
At the present time, numerous displays of this kind are equipped with means for adjusting the contrast, such adjustment being made at the beginning of a phase of use of the display and not being modified during this phase.
Now, it proves that for multiple reasons this method of adjustment does not allow optimum contrast to be obtained durably for the desired angle of vision.
First of all, it has been observed that, when he makes the adjustment, the operator is rarely in the position of use, so that the adjustment made is not optimum.
Furthermore, once the adjustment has been made, the contrast frequently varies for multiple reasons such for example as a variation of the temperature of the liquid crystal which is difficult to compensate for by temperature controlling the control voltage of the LCD. Moreover, variations of the threshold voltage of crystals from different suppliers, make this type of adjustment necessary.
It has also been proposed to adjust the liquid crystal cell so as to maintain the luminance of the light signals transmitted in a test zone substantially constant. However, such adjustment which is described in the "Patent Abstracts of Japan" vol 9, no. 62 (page 342) (1785), 19th May 1985, does not provide a contrast control.